# CVE-2026-104437: Zebra consensus divergence in V5 transparent signature verification

Source: https://junglewise.ai/threats/cve-2026-104437-zebra-before-4-4-0-contains-a-consensus-divergence-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-02. Updated: 2026-10-05  
License: CC BY 4.0 with a link back

CVE-2026-104437 · Severity: high · CVSS 7.4 · Published 2026-10-02

Zebra is a Zcash blockchain node implementation that validates transactions and creates mining templates. A flaw in how it verifies V5 transaction signatures causes it to accept transactions that the reference zcashd implementation rejects, potentially allowing miners to create blocks that the network won't accept, disrupting consensus and mining operations.

Technologies: [Zcash Foundation Zebra](https://junglewise.ai/threats/technologies/zebra). Vendors: [Zcash Foundation](https://junglewise.ai/threats/vendors/zcash-foundation).

## Quick answers

**Is CVE-2026-104437 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-104437 being exploited in the wild.

**How severe is CVE-2026-104437?** High severity, with a CVSS score of 7.4, published 2 October 2026.

**Which products and versions are affected?** Zcash Foundation Zebra before 4.4.0.

**Is there a fix for CVE-2026-104437?** Yes: fixed in 4.4.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-104437 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-104437?** Check whether you run Zcash Foundation Zebra at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 4.4.0

## Technical details

Zebra's ZIP-244 signature verification for SIGHASH_SINGLE transparent inputs fails to validate that input indices have corresponding outputs before computing the signature digest; instead it computes a digest for missing outputs. An attacker can craft a V5 transaction with more inputs than outputs, sign it using Zebra's incorrect digest computation, and Zebra will accept it into mempool and include it in getblocktemplate output, while zcashd rejects it at validation. The vulnerability requires network access and transaction creation capability, with no authentication needed; a fix is available in version 4.4.0.

## Affected products

- Zcash Foundation Zebra before 4.4.0

## Timeline

- 2026-05-02: disclosed
- 2026-10-02: advisory

## References

- [https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-cwfq-rfcr-8hmp](https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-cwfq-rfcr-8hmp)
- [https://www.vulncheck.com/advisories/zebra-before-4.4.0-consensus-split-via-sighash-single-missing-output-handling](https://www.vulncheck.com/advisories/zebra-before-4.4.0-consensus-split-via-sighash-single-missing-output-handling)

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